A WFC3/HST view of the three stellar populations in the Globular Cluster NGC6752

TL;DR

This study uses multi-band HST photometry to identify and characterize three distinct stellar populations within the globular cluster NGC6752, revealing their chemical compositions, relative proportions, and spatial distribution.

Contribution

It provides the first detailed photometric evidence for three separate stellar populations with distinct chemical signatures in NGC6752.

Findings

Three stellar populations with different chemical compositions identified.

Populations constitute approximately 25%, 45%, and 30% of the stars.

No radial gradient observed in population distribution.

Abstract

Multi-band Hubble Space Telescope photometry reveals that the main sequence, sub-giant, and the red giant branch of the globular cluster NGC6752 splits into three main components in close analogy with the three distinct segments along its horizontal branch stars. These triple sequences are consistent with three stellar groups: a stellar population with a chemical composition similar to field halo stars (population a), a population (c) with enhanced sodium and nitrogen, depleted carbon and oxygen and enhanced helium abundance (Delta Y ~0.03), and a population (b) with an intermediate (between population a and c) chemical composition and slightly helium enhanced (Delta Y ~0.01). These components contain ~25% (population a), ~45% (population b), and ~30% (population c) of the stars. No radial gradient for the relative numbers of the three populations has been identified out to about 2.5 half mass radii.